Fluorescent emulsion of indocyanine green

Abstract

The present invention relates to a formulation of indocyanine green in the form of a nanoemulsion, comprising a continuous aqueous phase and at least one dispersed oily phase, in which the oily phase comprises indocyanine green, at least one amphiphilic lipid and at least one solubilising lipid.It relates also to a process for the preparation and to the use of the formulation.

Description

[0001]The present invention relates to a novel formulation of indocyanine green which can be used as a diagnostic agent, in particular for fluorescence imaging, and to a process for the preparation thereof and uses thereof.PRIOR ART[0002]Fluorescence imaging is an imaging technique which is based on the injection of a fluorescent label into an animal or human and detection of the localisation of the fluorescent label. The instrumentation accordingly comprises an excitation source for the fluorescent label and a detector for the fluorescence emitted by the label.[0003]Nowadays, fluorescence imaging appears as a complementary imaging technique to other modalities such as MRI (magnetic resonance imaging), PET (positron emission tomography), SPECT (single photon emission computed tomography), ultrasonic echography, radiography or X-ray tomography.[0004]Fluorescence imaging has a number of advantages over the other imaging techniques:[0005]it does not use ionising rays and therefore does...

AI Technical Summary

Benefits of technology

The invention proposes a formulation of indocyanine green (ICG) in the form of a nanoemulsion, which has improved optical characteristics and can be used as a diagnostic agent. The nanoemulsion is stable and can be prepared in an isotonic medium, making it suitable for injection in humans. The formulation is easy to prepare, inexpensive, and can be adapted to different pharmaco-kinetics. It can also be functionalised and used for fluorescence imaging in clinical applications.

Problems solved by technology

However, ICG has some properties which render its use as a fluorescent label problematic.

First of all, ICG is an amphiphilic compound with a solubility of from 5 to 10 mg / ml and is therefore poorly soluble in water.

Moreover, ICG has poor stability and a low fluorescence quantum yield in aqueous solution, especially because of the formation of those poorly emissive dimers.

In addition, ICG is adsorbed on plasma proteins to a considerable degree when injected by the intravenous route, which alters the absorption and emission spectrum.

It is therefore difficult to distinguish the ICG fluorescence from the tissue autofluorescence using a fluorescence device based on pulsed luminous excitation.

Finally, liposomes are vesicles with a double-layer shell and generally have particle sizes greater than 100 nm in diameter; solutions of particles of that size diffuse light and do not permit satisfactory extravasation of the blood circulation to tumour tissues and internalisation in the cells.

However, formulations based on non-covalent adsorption bonds have low chemical stability and limit the choice of biological targeting ligands which can be used.

However, such synthetic liposomes are complicated to synthesise, require the use of synthetic polymers and do not directly yield nanoparticles suitable for permitting successful extravasation of the blood circulation to tumour tissues and internalisation in the cells, namely less than 100 nm and even less than 50 nm.

However, that type of formulation leads in most cases to emulsions in which the droplet size is too large to limit the diffusion of light and ensure satisfactory colloidal stability and furtivity after injection in vivo.

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